Pathogenic BRCA1 mutations disrupt allosteric control by BARD1

Area of Science:

• Biophysics
• Molecular Biology
• Cancer Research

Background:

• Pathogenic missense mutations in BRCA1 are linked to hereditary breast and ovarian cancer.
• The exact mechanism by which these mutations disrupt BRCA1's E3 ligase activity and lead to oncogenesis remains unclear.
• BRCA1's E3 ligase activity is activated by the binding of BARD1.

Purpose of the Study:

• To elucidate the mechanism by which BARD1 binding activates BRCA1's E3 ligase activity.
• To investigate how pathogenic mutations in BRCA1 affect its conformational states and E3 ligase activity.
• To identify potential therapeutic strategies for restoring BRCA1 function.

Main Methods:

• Atomistic molecular dynamics simulations.
• Markov state modeling.
• Allosteric coupling analysis.

Main Results:

• BARD1 binding selects for active conformational states of BRCA1.
• The BARD1 binding site (helix bundle) is allosterically coupled to the E2 interface.
• Pathogenic mutations destabilize these active states, while hyperactive mutations increase their likelihood.

Conclusions:

• BRCA1 pathogenesis is linked to BARD1-mediated selection of active conformational states.
• Pathogenic mutations disrupt this process by allosterically destabilizing active states.
• These findings provide a mechanistic basis for designing small molecule therapeutics to restore BRCA1 function.